With 6-men Syzygy.
I can confirm that even with 5-men Syzygy the solution is not easily found.

Looking at the variations, I think it's because of this kind of 6-men position:
[D]rn2R3/8/8/8/8/1PK5/8/6k1 w - - 0 6
Won for white, but you need a deep analysis to prove that without tablebases. The winning variation from this position is quite subtle, with the pawn providing coverage for the white King against rook checks.
Very pretty!

Stockfish seems to find No. 2 late on my computer, after 49 minutes. It is a bit changed engine though, just an experiment but the very latest codebase. I have not tried pure Stockfish or tablebases etc.